This disclosure relates to liquid crystal displays (LCDs), and more particularly, to LCDs having an enhanced light transmittance and improved lateral visibility.
LCDs are one of the more widely used types of flat panel displays, and typically include two substrates, or panels, having a plurality of field-generating electrodes, including pixel electrodes and a common electrode, arranged thereon, with a layer of a liquid crystal material being interposed between the two panels. LCDs control the transmittance of light incident on the panels by the application of selected voltages to the field-generating electrodes so as to generate electric fields, which determine the orientation of the liquid crystal molecules in the liquid crystal layer and thereby adjust the polarization of the light incident upon the panel.
One type of LCD that is currently receiving increased attention because of its high contrast ratio and wide reference viewing angle is referred to as a “vertical alignment” (VA) mode LCD, in which, in the absence of an electric field, the molecules of the liquid crystal layer are aligned such that the long axes of the molecules are oriented perpendicular to the panels. The wide viewing angle of the VA mode LCD is achieved by cutouts or protrusions formed in or on the field-generating electrodes.
In addition to the above VA mode LCDs, in another effort to improve lateral visibility, a “domain-division” type of LCD has been developed, in which the pixel regions thereof are divided into a plurality of domains so that the orientations of the liquid crystal molecules can be determined by cutouts or protrusions that enable the inclinations of the molecules to be distributed in various directions within the pixel, thereby widening the reference viewing angle. Since the direction in which the liquid crystal molecules are inclined can be determined by the use of cut portions and protrusions, the reference viewing angle can be widened by arranging the cut portions and the protrusions in such a way as to distribute the direction of inclination of the liquid crystal molecules in an optimum manner.
However, VA mode LCDs have relatively poor lateral visibility as compared to their frontal visibility. For example, a patterned VA (PVA) mode LCD having cutouts displays an image that becomes brighter at the sides thereof, thereby resulting in poor lateral visibility. To improve lateral visibility, a method has been proposed in which each pixel of the display is divided into two sub-pixels, and one of the two sub-pixels is directly supplied with a voltage, while the other is subjected to a voltage drop by capacitive coupling, such that the two sub-pixels have different voltages applied to them. However, this method can result in a degradation of the aperture ratio of the LCD due to the capacitive coupling of the sub-pixels, and the light transmittance of the display may be decreased due to the reduction in the average voltage of each of the respective sub-pixels.